Control of Metal Cold Forming Machines

ABSTRACT

A metal forming machine for cold forming a metal product to a desired dimension and/or configuration includes a forming means with at least one movable part for applying load to the metal product. A position sensing means establishes a measured position of the movable part indicative of a measured dimension and/or configuration of the metal product, and a load measuring means establishes a measured load applied by the moving part. A control means selects a nominal load (nom load) setting to achieve the desired dimension and/or configuration (pos nom), and enables actuation of the forming means until a calibration load (cal load) is reached where the position sensing means establishes the measured dimension and/or configuration (pos cal), whereupon the load is lowered. The control means then establishes a new load setting as a function of (pos nom) minus (pos cal), and reactivates the forming means to the new load setting to form the metal product.

FIELD OF THE INVENTION

The present invention relates to improvements in the control of cold forming metal working machines, particularly but not exclusively, swaging or crimping presses and metal folding or bending machines, to improve the accuracy of dimensions of the finally formed product.

BACKGROUND TO THE INVENTION

Machinery for cold forming metal, that is forming the metal in a non heated state suffers from dimensional accuracy of the product manufactured as a result of both machine strain and relaxation or springback of the metal formed. Metal when it is cold formed undergoes initially elastic deformation followed by plastic deformation, whereby, when the load is removed, at least a portion of the elastic deformation component recovers called metal springback. Such cold metal forming machines generally also operate with relatively high loadings to form the metal which places the forming machine under very high strains in reaction to these forces. As a result the forming machine will generally expand (called machine strain) in response to these operational forces. The measurement systems associated with such metal forming machines are usually attached to or engaged by at least one member that is subjected to these machine strain forces generated during a metal forming operation, and as a result, further inaccuracies are introduced into the correct dimensioning of the product produced. One solution to inaccuracies arising from machine strain causing movement in the machine structure is to make the machine structure ever more solid or strong such that the strain created movement is limited. This, however, results in machines that are bigger, heavier and more costly than they need to be.

The present invention will be described hereafter in the context of a metal swaging or crimping press where metal ferrules or casings are radially plastically deformed inwardly to clamp around a hose, tube or similar, however it should be appreciated that the invention has much wider application to cold metal forming machines generally including metal bending and folding machines. In swaging or crimping presses, a calibration procedure is commonly employed where a hardened solid billet of a reference diameter is inserted into the press zone of the swaging or crimping press. The press structure may typically have a position measurement device such as a potentiometer mounted from the front wall of the press which establishes the position of the press actuating hydraulic piston member. The front wall of the press is, however, subject to machine strain forces. The conventional calibration procedure is to load the press with the solid reference billet in place to one third of its rated loading ability and this point then becomes the reference point for future settings.

This calibration procedure compensates, to some extent, the springback effect and the machine strain effect with the swaging or crimping press but does not fully overcome the problem. Thus, for metal ferrules or casings that require less than one third applied pressure for proper deformation, the finished diameter of the end product will be slightly smaller than the installed or selected setting. For metal ferrules or casings requiring more than one third applied pressure for proper deformation, the finished diameter of the end product will be slightly larger than the installed or selected setting. It is only for metal ferrules or casings where the required forming pressure is substantially one third applied pressure where the finished diameter of the end product will be substantially correct.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide an arrangement and/or a process in a cold metal forming machine that will enable finished dimensions of a formed metal product to be substantially consistent with a machine selected dimensional setting for the product being formed.

Accordingly, the present invention provides a metal forming machine for plastically cold forming a metal product to a desired dimension and/or configuration, said machine including:

a forming means including a movable part for applying load to a metal product to cold form said metal product therefrom during a forming operation;

a position sensing means for establishing a measured position of said movable part indicative of a measured dimension and/or configuration of the metal product to be formed;

a load measuring means for establishing a measured load applied by said forming means during a said forming operation;

control means enabling actuation of said forming means including means for selecting a nominal load (nom load) setting to achieve the desired dimension and/or configuration (pos nom), said control means enabling actuation of said forming means until a calibration load (cal load) is reached where the position sensing means establishes a said measured dimension and/or configuration (pos cal) at said (cal load), whereupon the load is lowered, said control means establishing a new load setting as a function of the difference between (pos nom) and (pos cal), and said control means thereafter reactivating said forming means to said new load setting to form said metal product with the desired dimension and/or configuration, and said control means acting to remove said load thereafter.

By utilising a control means as outlined above, forming machines can be produced that will consistently produce the desired dimensions for the metal formed product without the need to produce excessively heavy, strong and costly machines. Moreover, the control means also provides compensation for metal springback effects.

Preferably the control means includes recording means to record the measured dimension and/or configuration established by said position sensing means, at least at said new load setting reached after reactivation of said forming means. Conveniently, the recording means provides reproducible data effectively showing the finished measured dimension and/or configuration.

The control means may include a microprocessor. Conveniently the forming operation occurs within the range of 100-2000 milliseconds, preferably about 500 milliseconds. Preferably the calibration load (cal load) is no more than 20% of said nominal load (nom load), preferably about 10% of said nominal load (nom load).

In a particularly preferred embodiment, the metal forming machine is a swage or crimping press, the forming means including a plurality of press jaws surrounding a press zone and adapted to move inwardly into the press zone during a said forming operation. The forming means of the aforesaid swage or crimping press may include a hydraulically operated piston means to radially simultaneously move said press jaws into said press zone during a said forming operation.

In accordance with a further aspect of this invention there is provided a method of plastically cold forming a metal work product such as an annular metal ferrule or casing in a press zone of a crimping or swaging press having a plurality of press jaws movable for applying load to the metal work product, said press further including a position sensing means for sensing an effective position of said press jaws indicative of a measured dimension and/or configuration of the work product, said press also including a load measuring means for establishing a measured load applied by said press jaws during a cold forming process, said method including the steps of selecting a nominal load (nom load) setting to achieve a desired dimension and/or configuration (pos nom), actuating the press jaws until a calibration load (cal load) is reached where the position sensing means establishes a measured dimension and/or configuration (pos cal) at said (cal load), lowering the load on said press jaws, establishing a new load setting as a function of the difference between (pos nom) and (pos cal), reactivating the press jaws to the new load setting to form said work product with the desired dimension and/or configuration, and thereafter removing load from said press jaws.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1 to 5 are schematic representations of apparatus according to the present invention sequentially carrying out the steps of cold forming an annular metal work product in a crimping or swaging press; and

FIG. 6 is a graphical representation of the measured deformed distance (d) of the metal work product of FIGS. 1 to 5 being pressed by the swaging or crimping press against time (t).

DESCRIPTION OF PREFERRED EMBODIMENTS

The following description is of a preferred embodiment of a swaging or crimping press (10) illustrated schematically in FIGS. 1 to 5 for applying a product (11) such as metal ferrules or casings to hoses, tubes or the like (12). Such presses commonly include a housing (13) with an annular side wall (14) and a front wall (15) with a product opening (16) therein permitting access to a press zone (14)/(17) where the forming process occurs. The press zone (17) is generally within the annular side wall (14) of the housing (13) and a forming means (18) is provided arranged therein consisting of a plurality of press jaws (19) arranged around the press zone (14) with an actuating position member driving the press jaws (19) radially inwardly under hydraulically applied forces during a forming operation. A position sensor device such as a potentiometer (20) extends through the front wall and senses the position of the piston member which indirectly establishes a measurement of the product (11) being formed in the press zone (14). The press (10) further includes a load measuring device, ie the load applied to a work piece in the press zone (14). In such presses (10), it is generally desired to form metal products (11) having a deformed finished diameter size within relatively close tolerances, particularly when performance of the hose (12) to which the metal product (11) is attached is critical.

In order to achieve finished ferrule or casing (11) diameters that are consistent with a selected installed setting, a control system (21) is provided which compensates for both machine strain and metal springback effects, hereafter referred to as a “compensator”. The “compensator” (21) requires a control device, typically but not exclusively an electronic control processor installed into the press as well as a device to register radial load. Further, a modification to the normal calibration procedure is required.

A Swage/Crimp press (10) installed with the “compensator” control (21) may be calibrated in a different manner. The Swage/Crimp press has a hardened dowel (22) (FIG. 1) introduced into the press zone (14) and rather than being loaded to ⅓ of its rated capability, it is loaded typically to 1/10 (but not limited to) of its rated capability. This load (load cal) and position (pos cal) becomes the reference point for the compensator (21). It is desirable that the calibration loading be as low as possible.

The functionality of the compensator (21) is as follows. A metal ferrule or casing is installed into the Swage/Crimp press (10) (FIG. 2) with a desired diameter setting also being specified. The press (10) is operated and the metal ferrule or casing is formed to a diameter somewhat less than the desired setting due to the modified calibration procedure.

At the end of this procedure, the load in the swage press (10) is lowered in a controlled manner. When the load measuring device detects a load that matches the calibration load (load cal), the compensator will reference the measured metal casing reading to that of (pos cal) from the calibration procedure and calculate a modified setting value.

The press (10) then re-activates and re-forms the metal casing to the calculated, modified setting. The press (10) will again unload in a controlled manner. When the load measuring device detects a load that matches (load cal) the springback compensator will again reference the metal casing reading to that of (pos cal) and this time calculate an actual measured diameter either in millimetre or inch value.

This value may be stored in a database and accessed if required. The storing of this value is not an essential feature of the compensator.

The press will then open either automatically or manually, and the metal casing can be removed.

With reference to FIG. 6, the Swage/Crimp press (10) is operated from 1 to 2 to reduce the metal ferrule or casing to a required measured radial dimension (a), bearing in mind the dimension of the ferrule or casing (11) will be subject to elastic springback and machine strain potential errors. From position 2 to position 3, the Swage/Crimp (10) press is subject to a controlled reduction in applied loading with retraction of the radial forces applied by the die jaws (19) until the radial force equals the calibration loading force at measured dimension (b). The compensator (21) calculates the dimension difference (b)−(a). The crimping or swaging action is then recommenced from position (3) to position (4) with the new target point (c) equalling (a)−((b)−(a)) with the metal ferrule or casing (11) being reduced to the new diameter (c). The process then from 4 to 5 involves a second controlled reduction in applied hydraulic crimping/swaging loading until the applied loading on the die jaws (19) again equals the calibrator loading (at 5). The diameter (d) is then rechecked and compared to the desired diameter (a) to determine whether it is within the allowed tolerance deviations from the desired diameter (a). If it is, then the dimension (d) may be recorded so that it can be reproduced, if desired, and the forming process is terminated. If it is not within allowable tolerance deviations, then the process from 3 to 5 is repeated, at least once, but possibly more than once, until the measured diameter is within allowable tolerance deviations. Once this point is achieved, the forces applied to the die jaws (19) can be removed totally with the die jaws (19) being fully retracted to position (6) on the graph (FIG. 6) to allow the formed metal ferrule/casing to be removed.

The operation of the compensator (21) as described from 3 to 5 preferably may operate within a range of 100 to 2000 milliseconds, but preferably about 500 milliseconds. Also, it should only require one referencing operation to provide the required accuracy but in some instances as discussed above, the control system may implement two or more referencing operations depending on the required accuracy required. 

1. A metal forming machine for plastically cold forming a metal product to a desired dimension and/or configuration, said machine including: a forming means including a movable part for applying load to a metal product to cold form said metal product therefrom during a forming operation; a position sensing means for establishing a measured position of said movable part indicative of a measured dimension and/or configuration of the metal product to be formed; a load measuring means for establishing a measured load applied by said forming means during a said forming operation; control means enabling actuation of said forming means including means for selecting a nominal load (nom load) setting to achieve the desired dimension and/or configuration (pos nom), said control means enabling actuation of said forming means until a calibration load (cal load) is reached where the position sensing means establishes a said measured dimension and/or configuration (pos cal) at said (cal load), whereupon the load is lowered, said control means establishing a new load setting as a function of the difference between (pos nom) and (pos cal), and said control means thereafter reactivating said forming means to said new load setting to form said metal product with the desired dimension and/or configuration, and said control means acting to remove said load thereafter.
 2. A metal forming machine according to claim 1 wherein the control means includes recording means to record the measured dimension and/or configuration established by said position sensing means, at least at said new load setting reached after reactivation of said forming means.
 3. A metal forming machine according to claim 2 wherein the recording means provides reproducible data effectively showing the finished measured dimension and/or configuration.
 4. A metal forming machine according to claim 1 wherein the control means includes a microprocessor.
 5. A metal forming machine according to claim 1 wherein the forming operation occurs within the range of 100 to 2000 milliseconds, preferably about 500 milliseconds.
 6. A metal forming machine according to anyone of claim 1 wherein the calibration load (cal. load) is no more than 20% of said nominal load (nom. load), preferably about 10% of said nominal load (nom. load).
 7. A metal forming machine according to claim 1 wherein the metal forming machine is a swage or crimping press, the forming means including a plurality of press jaws surrounding a press zone and adapted to move inwardly into the press zone during a said forming operation.
 8. A metal forming machine according to claim 7 wherein the forming means of the press includes a hydraulically operated piston means to radially simultaneously move said press jaws into said press zone during a said forming operation.
 9. A method of plastically cold forming a metal work product such as an annular metal ferrule or casing in a press zone of a crimping or swaging press having a plurality of press jaws movable for applying load to the metal work product, said press further including a position sensing means for sensing an effective position of said press jaws indicative of a measured dimension and/or configuration of the work product, said press also including a load measuring means for establishing a measured load applied by said press jaws during a cold forming process, said method including the steps of: selecting a nominal load (nom load) setting to achieve a desired dimension and/or configuration (pos nom), actuating the press jaws until a calibration load (cal load) is reached where the position sensing means establishes a measured dimension and/or configuration (pos cal) at said (cal load), lowering the load on said press jaws, establishing a new load setting as a function of the difference between (pos nom) and (pos cal), reactivating the press jaws to the new load setting to form said work product with the desired dimension and/or configuration, and thereafter removing load from said press jaws. 